How to get glare on a specific emission reflection
You basically need to have some way to get only the reflection so that you can perform some effect on it (e.g., glare or blurring the reflection and adding it to the image). You could use color keying if you can't see anything else that is red, you could map an object to the screen of the red dot that was on a different layer only used for compositing, and you can also provide access to the glossy reflections in the compositor. Actually, all three techniques can be used to do this in a more universal manner, but depending on your situation, you will have to make the best choice. 

Here is an example I just made:


Enable glossy direct in render layers





My compositor node setup (could be much improved...I just blur the bright parts of the reflection)





Result 




Blend file: